CN110729761A - Grid-connected and off-grid switching circuit and method of photovoltaic inverter - Google Patents
Grid-connected and off-grid switching circuit and method of photovoltaic inverter Download PDFInfo
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- CN110729761A CN110729761A CN201911098493.6A CN201911098493A CN110729761A CN 110729761 A CN110729761 A CN 110729761A CN 201911098493 A CN201911098493 A CN 201911098493A CN 110729761 A CN110729761 A CN 110729761A
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/50—Photovoltaic [PV] energy
- Y02E10/56—Power conversion systems, e.g. maximum power point trackers
Abstract
The invention discloses a grid-connected and off-grid switching circuit and method of a photovoltaic inverter, which can realize the working state switching of an energy storage inverter by controlling the opening and closing of 8 relays, thereby reducing the cost, reducing the loss and improving the efficiency. The relay group of the grid-connected and off-grid switching circuit consists of 8 relays; the first main relay and the first auxiliary relay are sequentially connected between the inverter and the load in series; the second main relay and the second auxiliary relay are sequentially connected between the inverter and the load in series; one end of the first load relay and one end of the second load relay are mutually connected in series, the other end of the first load relay is connected to a connection point of the first auxiliary relay and the load, and the other end of the second load relay is connected to a power grid; one end of the third load relay and one end of the fourth load relay are connected in series, the other end of the third load relay is connected to a connection point of the second auxiliary relay and the load, and the other end of the fourth load relay is connected to the power grid.
Description
Technical Field
The invention belongs to the field of photovoltaic grid-connected inverters, and relates to a grid-connected and off-grid switching circuit and method of a photovoltaic inverter.
Background
The photovoltaic grid-connected inverter is used for converting direct current generated by the solar panel into alternating current to be directly transmitted to a power grid or supplied to a load, namely, the output end of the inverter is electrically connected with the power grid and the load directly or through a transformer and the like. In order to meet the safety requirement, the safety requirement is that a plurality of groups of relays are required to be connected in series at the output end of the inverter and the input end of the power grid, a plurality of groups of relays are required to be connected in series at the output side of the inverter and the input end of the load, and the like, so that the inverter can be timely and reliably disconnected from the power grid when the system is abnormal. Referring to fig. 1, in a conventional solution, at least 12 RELAYs need to be arranged, where 4 inverters 1 to 4 of a power grid (main RELAY and auxiliary RELAY), 4 inverters 1 to 3 loads (off-grid RELAY), and 4 other inverters 4 to 3 loads (load ELAY) are required to implement grid-connection and off-grid switching of the energy storage inverter 1, and the topology is complex, the cost is high, the loss is large, and the efficiency is low.
Disclosure of Invention
In order to solve the technical problems, the invention aims to provide a grid-connected and grid-disconnected switching circuit and a method for a photovoltaic inverter, which can realize the switching of the working states of an energy storage inverter by controlling the opening and closing of 8 relays on the premise of meeting the safety regulation requirements, thereby reducing the cost, reducing the loss and improving the efficiency.
In order to achieve the purpose, the invention adopts the following technical scheme:
a grid-connected and off-grid switching circuit of a photovoltaic inverter comprises a relay group;
the relay group consists of a first main relay, a second main relay, a first auxiliary relay, a second auxiliary relay, a first load relay, a second load relay, a third load relay and a fourth load relay;
the first main relay and the first auxiliary relay are sequentially connected in series between the inverter and an input line L of a load; the second main relay and the second auxiliary relay are sequentially connected in series between the inverter and an input line N of a load;
one end of the first load relay and one end of the second load relay are connected in series, the other end of the first load relay is connected to a connection point of the first auxiliary relay and an input line L of the load, and the other end of the second load relay is connected to an input line L1 of a power grid;
one end of the third load relay and one end of the fourth load relay are connected in series with each other, the other end of the third load relay is connected to a connection point of the second sub-relay and an input line N of the load, and the other end of the fourth load relay is connected to an input line L2 of a power grid.
Herein, the connection point of two components (e.g., the second auxiliary relay and the input line N of the load) refers to any point between the two components, and specifically, any point of the conductive medium electrically connected between the two components.
Preferably, the grid-connected and grid-disconnected switching circuit has a grid-connected working mode, an off-grid working mode and a bypass mode;
when the grid-connected and off-grid switching circuit is in a grid-connected working mode, the first main relay, the second main relay, the first auxiliary relay, the second auxiliary relay, the first load relay, the second load relay, the third load relay and the fourth load relay are all in a closed state;
when the grid-connected and grid-disconnected switching circuit is in the grid-disconnected working mode, the first main relay, the second main relay, the first auxiliary relay and the second auxiliary relay are in a closed state, and the first load relay, the second load relay, the third load relay and the fourth load relay are in an open state;
when the grid-connected and grid-disconnected switching circuit is in a bypass mode, the first main relay, the second main relay, the first auxiliary relay and the second auxiliary relay are in an off state, and the first load relay, the second load relay, the third load relay and the fourth load relay are in a closed state.
The invention also adopts the following technical scheme:
the grid-connected and off-grid switching method of the grid-connected and off-grid switching circuit of the photovoltaic inverter comprises the following steps:
closing the first main relay, the second main relay, the first auxiliary relay, the second auxiliary relay, the first load relay, the second load relay, the third load relay and the fourth load relay to enable the grid-connected and off-grid switching circuit to be in a grid-connected working mode, and enabling the photovoltaic inverter to be in grid-connected working;
closing the first main relay, the second main relay, the first auxiliary relay and the second auxiliary relay, and disconnecting the first load relay, the second load relay, the third load relay and the fourth load relay to enable the grid-connected and grid-disconnected switching circuit to be in an off-grid working mode, and enable the photovoltaic inverter to work off-grid;
and disconnecting the first main relay, the second main relay, the first auxiliary relay and the second auxiliary relay, closing the first load relay, the second load relay, the third load relay and the fourth load relay, and supplying power to the load by a power grid.
Compared with the prior art, the invention has the following advantages by adopting the scheme:
in the invention, on the premise of meeting the requirement of safety regulations, only 8 relays are used, and the relays in the grid-connected state multiplex the relays in the off-grid state and the relays in the bypass state, so that compared with the prior art, 4 relays are reduced, the cost is reduced by one third, the loss is greatly reduced, and the efficiency of the whole machine is improved. Meanwhile, because the number is reduced, the detection logic of the relay is simple, and the reliability of software and hardware is greatly improved.
Drawings
In order to more clearly illustrate the technical solution of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.
Fig. 1 is a schematic diagram of a grid-connected and off-grid switching circuit of a conventional photovoltaic inverter;
fig. 2 is a schematic diagram of a grid-connected and off-grid switching circuit of a photovoltaic inverter according to an embodiment of the invention.
Wherein:
1. an inverter;
2. a relay group; 21. a first main relay; 22. a second main relay; 23. a first auxiliary relay; 24. a second auxiliary relay; 25. a first load relay; 26. a second load relay; 27. a third load relay; 28. fourth load relay
3. A load;
4. and (4) a power grid.
Detailed Description
Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings so that the advantages and features of the invention may be more readily understood by those skilled in the art. It should be noted that the description of the embodiments is provided to help understanding of the present invention, but the present invention is not limited thereto. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
The embodiment provides a grid-connected and off-grid switching circuit of a photovoltaic inverter, which is suitable for switching the working mode of the inverter in a photovoltaic energy storage inverter. Referring to fig. 2, the grid-connected and grid-disconnected switching circuit includes a relay group 2, and the relay group 2 is disposed between the inverter 1 and the load 3, and the grid 4. The relay group 2 is composed of a first main relay 21, a second main relay 22, a first auxiliary relay 23, a second auxiliary relay 24, a first load relay 25, a second load relay 26, a third load relay 27 and a fourth load relay 28, and is composed of only 8 relays.
The first main relay 21 and the first auxiliary relay 23 are sequentially connected in series between the inverter 1 and the input line L of the load 3; the second main relay 22 and the second sub-relay 24 are connected in series between the inverter 1 and the input line N of the load 3 in this order. That is, the first main relay 21 and the first sub-relay 23 are connected in series with each other, and the second main relay 22 and the second sub-relay 24 are connected in series with each other, these four relays being provided between the inverter 1 and the load 3.
One end of the first load relay 25 and one end of the second load relay 26 are connected in series, the other end of the first load relay 25 is connected to a connection point of the first sub-relay 23 and an input line L of the load 3, and the other end of the second load relay 26 is connected to an input line L1 of the grid 4; one end of the third load relay 27 and one end of the fourth load relay 28 are connected in series, the other end of the third load relay 27 is connected to a connection point of the second sub-relay 24 and the input line N of the load 3, and the other end of the fourth load relay 28 is connected to the input line L2 of the grid 4. That is, the first load RELAY 25 and the second load RELAY 26 are connected in series with each other, and the third load RELAY 27 and the fourth load RELAY 28 are connected in series with each other, and these four RELAYs are provided as the load RELAY on the front side of the grid 4. Herein, the connection point of two components (e.g., the second auxiliary relay 24 and the input line N of the load 3) refers to any point between the two components, specifically, any point of the conductive medium electrically connected between the two components.
The grid-connected and off-grid switching circuit has a grid-connected working mode, an off-grid working mode and a bypass mode:
when the grid-connected and grid-disconnected switching circuit is in a grid-connected working mode, the first main relay 21, the second main relay 22, the first auxiliary relay 23, the second auxiliary relay 24, the first load relay 25, the second load relay 26, the third load relay 27 and the fourth load relay 28 are all in a closed state, and the photovoltaic inverter 1 works in a grid-connected state;
when the grid-connected and grid-disconnected switching circuit is in the grid-disconnected working mode, the first main relay 21, the second main relay 22, the first auxiliary relay 23 and the second auxiliary relay 24 are in a closed state, the first load relay 25, the second load relay 26, the third load relay 27 and the fourth load relay 28 are in an open state, and the photovoltaic inverter 1 works in the grid-disconnected state;
when the grid-connected and grid-disconnected switching circuit is in a bypass mode, the first main relay 21, the second main relay 22, the first auxiliary relay 23 and the second auxiliary relay 24 are in an off state, the first load relay 25, the second load relay 26, the third load relay 27 and the fourth load relay 28 are in an on state, the photovoltaic inverter 1 is in a bypass state, and the power is directly supplied to the load 3 by the grid 4.
The embodiment also provides a grid-connected and off-grid switching method of the grid-connected and off-grid switching circuit of the photovoltaic inverter 1. The grid-connected and off-grid switching method of the photovoltaic inverter 1 is applied to a grid-connected and off-grid switching circuit shown in fig. 2, and specifically comprises the following steps:
closing the first main relay 21, the second main relay 22, the first auxiliary relay 23, the second auxiliary relay 24, the first load relay 25, the second load relay 26, the third load relay 27 and the fourth load relay 28 to enable the grid-connected and grid-disconnected switching circuit to be in a grid-connected working mode, and enabling the photovoltaic inverter 1 to work in a grid-connected mode;
closing the first main relay 21, the second main relay 22, the first auxiliary relay 23 and the second auxiliary relay 24, and opening the first load relay 25, the second load relay 26, the third load relay 27 and the fourth load relay 28, so that the grid-connected and grid-disconnected switching circuit is in a grid-disconnected working mode, and the photovoltaic inverter 1 is in grid-disconnected working;
the first main relay 21, the second main relay 22, the first sub relay 23, and the second sub relay 24 are opened, the first load relay 25, the second load relay 26, the third load relay 27, and the fourth load relay 28 are closed, and the power is supplied to the load 3 from the grid 4.
In the grid-connected and off-grid switching circuit and the method, only 8 relays are used, 4 relays are used from the inverter to the load and 4 relays are used from the power grid to the load in the off-grid state, and 8 relays are used from the inverter to the power grid in the grid-connected state. The relay in the grid-connected state multiplexes the relays in the off-grid state and the bypass state, and 4 relays are reduced. The number of the relays is reduced from 12 to 8, the cost is reduced by one third, the loss is greatly reduced, and the efficiency of the whole machine is improved. Meanwhile, due to the fact that the number of the relay detection circuits is reduced, the relay detection logic is simple, and the reliability of software and hardware is greatly improved.
The above embodiments are merely illustrative of the technical ideas and features of the present invention, and are preferred embodiments, which are intended to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and not to limit the scope of the present invention. All equivalent changes or modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.
Claims (3)
1. A grid-connected and off-grid switching circuit of a photovoltaic inverter comprises a relay group; the method is characterized in that:
the relay group consists of a first main relay, a second main relay, a first auxiliary relay, a second auxiliary relay, a first load relay, a second load relay, a third load relay and a fourth load relay;
the first main relay and the first auxiliary relay are sequentially connected in series between the inverter and an input line L of a load; the second main relay and the second auxiliary relay are sequentially connected in series between the inverter and an input line N of a load;
one end of the first load relay and one end of the second load relay are connected in series, the other end of the first load relay is connected to a connection point of the first auxiliary relay and an input line L of the load, and the other end of the second load relay is connected to an input line L1 of a power grid;
one end of the third load relay and one end of the fourth load relay are connected in series with each other, the other end of the third load relay is connected to a connection point of the second sub-relay and an input line N of the load, and the other end of the fourth load relay is connected to an input line L2 of a power grid.
2. The grid-connected and grid-disconnected switching circuit according to claim 1, wherein: the grid-connected and off-grid switching circuit has a grid-connected working mode, an off-grid working mode and a bypass mode;
when the grid-connected and off-grid switching circuit is in a grid-connected working mode, the first main relay, the second main relay, the first auxiliary relay, the second auxiliary relay, the first load relay, the second load relay, the third load relay and the fourth load relay are all in a closed state;
when the grid-connected and grid-disconnected switching circuit is in the grid-disconnected working mode, the first main relay, the second main relay, the first auxiliary relay and the second auxiliary relay are in a closed state, and the first load relay, the second load relay, the third load relay and the fourth load relay are in an open state;
when the grid-connected and grid-disconnected switching circuit is in a bypass mode, the first main relay, the second main relay, the first auxiliary relay and the second auxiliary relay are in an off state, and the first load relay, the second load relay, the third load relay and the fourth load relay are in a closed state.
3. The grid-connection and off-grid switching method of the grid-connection and off-grid switching circuit of the photovoltaic inverter according to claim 1 or 2, characterized by comprising the following steps:
closing the first main relay, the second main relay, the first auxiliary relay, the second auxiliary relay, the first load relay, the second load relay, the third load relay and the fourth load relay to enable the grid-connected and off-grid switching circuit to be in a grid-connected working mode, and enabling the photovoltaic inverter to be in grid-connected working;
closing the first main relay, the second main relay, the first auxiliary relay and the second auxiliary relay, and disconnecting the first load relay, the second load relay, the third load relay and the fourth load relay to enable the grid-connected and grid-disconnected switching circuit to be in an off-grid working mode, and enable the photovoltaic inverter to work off-grid;
and disconnecting the first main relay, the second main relay, the first auxiliary relay and the second auxiliary relay, closing the first load relay, the second load relay, the third load relay and the fourth load relay, and supplying power to the load by a power grid.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201911098493.6A CN110729761A (en) | 2019-11-12 | 2019-11-12 | Grid-connected and off-grid switching circuit and method of photovoltaic inverter |
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| Application Number | Priority Date | Filing Date | Title |
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| CN201911098493.6A CN110729761A (en) | 2019-11-12 | 2019-11-12 | Grid-connected and off-grid switching circuit and method of photovoltaic inverter |
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| CN110729761A true CN110729761A (en) | 2020-01-24 |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112952819A (en) * | 2021-03-19 | 2021-06-11 | 江苏固德威电源科技股份有限公司 | Split-phase output fast switching circuit and control method for restraining surge current adopted by same |
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2019
- 2019-11-12 CN CN201911098493.6A patent/CN110729761A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112952819A (en) * | 2021-03-19 | 2021-06-11 | 江苏固德威电源科技股份有限公司 | Split-phase output fast switching circuit and control method for restraining surge current adopted by same |
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